1. Field of the Invention
The invention relates to a roll, a calender and a process for operating a roll, and more particularly, to a roll with a core that has an elastic cover extending over a working width and with roller pins on the end faces of the core.
2. Discussion of Background Information
Calender rolls having an elastic cover have been used as a middle roll in a roll stack of a calender. These rolls are often called a soft or elastic calender roll, because the cover causes the surface of the roll to be elastic to a certain degree. A calender roll of this kind cooperates with a "hard" roll in order to satinate a paper web or another material web.
The hard roll is often heated so that the paper web can be acted on with increased pressure and increased temperature in the nip formed between the soft roll and the hard roll. The elastic cover is used primarily for uniform compression of the paper web.
The working width of such a calender roll corresponds to the width of the material web to be treated. The cover can taper conically outside the working width. This tapering extends over an axial length in the size range of approximately 20 to 100 mm. This length prevents the part of the cover that is not covered by a paper web from coming into contact with the counter roll and being damaged. For future reference, only the working region of the cover is referred to as the working width.
Rolls are often damaged during operation because the cover tears or breaks. This damage occurs even in very temperature-resistant or temperature-proof covers that are actually supposed to withstand the temperatures during operation.
Working with heat-carrying mediums is intrinsically known in the related art, for example, from cooling or heating rolls. However, these rolls do not have an elastic cover. Heretofore, when elastic rolls have been temperature controlled, this control occurred by using air to cool the cover.